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Патент USA US2137199

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Nov. 15, 1938*.
P. l.. BE-rz
2,137,199
CONTROL SYSTEM FOR GAS HEATERS
Filed Aug. 30, 1935
2 Sheéts-Shee‘l‘. 1
RIIAY
CONTMTS
Nov. 15, 1938.
P. L. BETZ
2,137,199
CONTROL SYSTEM FOR GAS HEATERS
Filed Aug. 50, 1935
gul/ë
2 Sheets-Sheet 2
,
'
2,131,199
` Patented Nov. 15, 1938
UNITED STATESv
PATENT ‘ OFFICE
2,137,199
CONTROL SYSTEM'. FOR GAS HEATERS'
l Paul L. Betz, Baltimore, Md., assignor to- Con
solidated Gas Electric Light and Power Com
pany of Baltimore, Baltimore, Md., a corpora
tion of Maryland
v Application August so, 1935, serial No. 38,656
9 Claims. (Cl. 15S-_28)
This invention relates to electrical control gas heater which embodies both operating con
systems for gas heaters 'such for example as gas trols and safety devices and which is a unit in
itself for automatic control and regulation of
water heaters and the like.
Gas heating systems usually are required to the heater.
'
Another object is to provide a novel control 5
5 operate reliably and without attention in service
over long periods and it is desirable to provide system of the type characterized above which
can be set in operation either locally or remotely
them with adequate safeguards against the dan
and either automatically or manually.
.
ger of explosions, leaking gas, improper com
A further object is to provide a novel electrica
bustion, etc., in the event of abnormal condi
10 tions. ‘For example, in thermostatically con
trolled or remotely controlled systems having a
pilot ilame, there is the danger of turning on
the gas when for some reason the pilot is not
functioning properly. Another abnormal con
15 dition involving elements of danger is what is
termed a flashback wherein the flame ñashes
back through the burner orifices and burns in
the chamber in which the mixture of gas and air
normally takes place, resulting in failure ofthe
2o system to operate properly and in incomplete
combustion with production of carbon monoxide.
Also, there is danger of damage to the system
in the event that the temperature of the water'
_
or other substance to be heated becomes ‘exces
25 sive. To safeguard against these and other dan
control system for a gas heater which embodies 10
both operating and safety controls and which is
complete in itself for automatic control and reg
ulation of the heater and is adapted for energi
zation or deenergization merely by operating a
suitable circuit closing device.
15
A still further object is to provide a novel elec
trical control system for a gas heater which em
bodies a single electrically controlled gas valve
and an electrical control system for said valve
whereby it performs the functions of a supply 20
valve and in addition of a safety valve operable _
to shut oil the gas ‘or inoperative to turn on the ,
gas in the event of various abnormal conditions
of operation of the heater.
Another object is to provide a novel control 25
system for a gas heater wherein various .electri
gers, various means have been devised hereto
fore, but in general, such devices have been de- ' cal devices are combined in a single electrical
signed individually each with respect to a par
ticular condition without particular regard to
30 the correlation of various safety devices into one
system. The use of a plurality of such devices
in one system hence tends to a multiplicity of
individual controls and equipment, in many cases
_of different types and with increased cost.
35
Further, automatic or senil-automatic opera
tion of such systems is loften desirable. For ex
ample, it is desirable in many cases to operate a
control system automatically and continuously in
such manner as to maintain a constant tem
40 perature of the water or other substance to be
heated. Also, it may be desired to _operate a
system automatically but only during certain
periods of the day, which periods may be deter
mined by suitable clock mechanism or at the
45 will of the user. Systems adapted to these ends
require automatically operating means for initi
system and connected by suitable circuits so as
to be energized from a common source and
through a common circuit closing device for op- 30
eration as a unit.
Three control systems embodying the inven
tion have been illustrated in the accompanying
drawings, but it is to be expressly understood
that said> drawings are for purpose of illustration 03 5
only and are not to be construed as a deiìnition
of the limits of the invention, reference being
had to the appended claims for this purpose.
In said drawings:
Fig. 1 is a diagrammatic view showing a gas
Water heater installation of conventional type
equipped with a control system embodying the
invention;
Fig. 2 is a sectional view of one form of elec
tric relay suitable for use in the system of Fig. 1; 45
Fig. 3 is a wiring diagram of another control
ating, controlling and stopping the operation of
the system, in additionto safety controls such
system embodying the invention; and
as those referred to above.
system embodying the invention.
The invention has been illustrated herein in Ul
In the interest of
Fig. 4-is a wiring diagram of another control
50 simplicity, economy and reliable and eiilcient op
eration, the operating controls should be corre
lated with the safety controls to facilitate their
combination in a complete unitary system.
One of the objects of the present invention is
the invention are not restricted to this particular
use but can be employed to regulate and control
55 to provide a novel electrical control system for a
the operation' of any gas heating installation. 55
connection with a gas water heater but it is to
be understood that control systems embodying
2
2,187,199
As shown herein. the heater comprises a tank or
boiler I having an inlet connection 2 for cold
water and an outlet connection 3 for hot water.
The water in the tank circulates through the
heater 4 containing the coil 8 by means of pipes
8 and 1. Gas is supplied to the gas burner 8
through a pipe 9 preferably provided with a
manually operable valve Ill. In the chamber II
the gas is mixed with air and the combustible
10 mixture of gas and air is then delivered to the
burner 8. Since this particular heating installa
tion is shown merely to illustrate the use of the
invention, its details need' not be described fur
ther herein.
The flow of gas to the heater is controlled by
15
a valve I2 located in the pipe 9, which valve is
electrically controlled.
Electrically controlled
and operated valves of various types are known
and can be obtained on the market. For ex
20 ample, one suitable type of such valve comprises
a valve member which tends to close either by
gravity or spring tension but is maintained open
by an electromagnet, and this type of valve is
assumed in the following description for purposes
25 of illustration. The control system described
hereinafter is therefore particularly adapted to
the regulation and operation of a valve of this
type in such a Way that it acts not only as an
automatic supply valve but also as a safety valve
30 under various abnormal conditions.
The electrical control system is energized by a
transformer I3, the circuit to which includes a
suitable circuit closing device such as the switch
I4. Since, as hereinafter described, the control
35 system energized by the transformer comprises
a, complete operating unit, the switch I4 is not
essential if the system is to operate continuously
and on the other hand, if intermittent opera
tion is desired, the switch may be controlled in
40 any suitable manner to cause the operation of
the system either periodically, or in accordance
with a. condition such as the water temperature,
or manually whenever operation is desired, and
it may be located at any desired point either ad
45 jacent to or remote from the system itself.
The operation of the system is primarily con
trolled by a relay which for purposes described
hereinafter involves time delayed operation.
While as respects the present invention any suit
50 able type of relay having such time delayed op
eration can be used in conjunction with the con
trol system, Fig. 2 illustrates as an example a
suitable relay forming the subject matter of the
prior application of Paul L. Betz, Serial No.
55 742,335, i'lled August 3l, 1934. Brieñy, this re
lay comprises an operating coil I5 provided with
leads I6 and I1 and a movable armature I8 con
nected in any suitable manner with an operat
ing rod I9. The armature I8 normally occupies
60 the position shown in the drawings and is so
disposed with respect to the winding energized
through leads I6, I1 that said winding is unable
to lift the armature until a supplementary wind
ing I5a is energized through leads 20 and 2|.
`es One of said leads 20 and 2i is connected in series
with normally open contacts 22, one of which is
carried by a bimetallic strip surrounded by a
heating coil 23. Accordingly, the armature »I8
70 is not actuated when current is first supplied to
the relay until after the interval necessary for
the coil 23 to heat the bimetallic strip and there
by to close the contacts 22. The relay also com
prises a pair of normally closed contacts 24 and
75 a pair of normally open contacts 25, which are
respectively opened and closed when the arma
ture is lifted.
,
-
.
A relay of this type is employed in control sys
tems embodying the present invention as a safety
device to prevent opening of the gas valve until
the electric pilot has had time to reach ignition
temperature. >'I‘his may be accomplished by con-`
trolling or operating the gas valve through the
relay contacts which are not closed until after
the time delay provided by the relay operation, 10
whereas the pilot device is energized with the
relay. The relay is thus the primary controlling
element in the normal operation of the system,
and the safety controls may suitably be arranged
in such a way as to prevent the energization of
the relay or to deenergize the same, in the event
of an abnormal condition, whereby the valve
either does not open or is closed as the case
may be.
-
A system of this type is illustrated in Fig. 1,
wherein the relay is diagrammatically shown at
26. It is provided with a pair of terminals 21
across which the normally open relay contacts
25 are connected. One of the terminals 21 is
connected to one side of the transformer sec
ondary by wires 28 and 29 whereas the other ter
minal 21 is connected to one of the terminals of
the valve I2 by a wire 30, the other valve termi
nal being connected to the other side of the
transformer secondary by wire 3|. Thus the en 30
ergizing circuit of the valve can be closed to open
said valve only after the relay armature is picked
up to close the contacts 25. Further, as soon
as the relay is deenergized, said armature re
turns to the position shown in Fig. 2 with the 35
result that contacts 25 open and permit valve I2
to close, shutting off the supply of gas to the
lburner 8.
‘
`
The valve I2 is adapted to function both as
a supply valve and as a safety valve by the in
corporation of suitable safety controls which
40
cause the interruption of the valve circuit in the
event of abnormal conditions of operation of the
heater. While these devices can be connected in
circuit with the valve in various ways, prefer 45
ably and as shown herein, they control the relay
input in such a. way that the relay is deener
g-ized in the event of operation of any of the
safety devices, so that when the abnormal con
dition no longer exists,.the valve must be opened. 50
again through operation of the relay. To this
end, one of the relay input terminals 32 is con
nected -to the wire 29 leading to one side of the
transformer secondary, and the other terminal
32 is connected to Wire 3l leading to the other
side of the transformer secondary through a. con
trol circuit which includes wires 33, 34 and 35.
Wires 34 and 35 are connected to the terminals
of a suitable thermostatic circuit closing device
36 which controls the operation of the relay so
as to prevent the temperature of the Water in
the tank I from becoming excessive. 'I'his ther
mostat may be of any suitable type which is
adapted to open the relay input circuit so as to
deenergize the same in the event that the tem
perature becomes excessive.
Wires 33 and 34 are connected to the terminals
of a suitable safety device operative to interrupt
the input circuit to the relay in the event of a
flashback from burner 8. While as respects the
control system claimed herein this’safety device
may be of any suitable form, as shown herein it
comprises one of the ñashback safety devices
disclosed in the copending application of Paul L.
Betz and Sebastian Karrer, Serial No. 38,654,
55
60
65
70
2,137,199
flied August 30, 1935. Briefly, the circuit between
23 and opening the valve I2 to supply gas to the
wires 33 and 34 is completed through a pair of
contacts 31 supported on resilient arms 33 which
tend to maintain said contacts open, the contacts
being normally maintained closed by a bi
metallic element 38 disposed within the mix
ing chamber Il and having an extension en-l
burner. 'I'he burner is ignited and the water
gaging one of the arms 33.
from the tank I circulates through the coil 6 and
is heated to the desired temperature or the op
eration is continued for the desired period at
which point the switch I4 is opened either auto
matically or manually.
In the case of a
In the event a flashback occurs at the burner
flashback, the temperature of the bimetallic
l, the flashback safety device causes contacts 31
10 element 39 is increased and said element bends
in such a direction as to permit arms 33 to open
the contacts 31 and thereby to deenergize the
relay.
_
The burner 8 is provided with an electric ig
15 -nition device or pilot 4I) preferably in the form of
a wire adapted to become incandescent.. said
wire being energized through leads 4I and 42
which may, ii desired, include fuses 43 and which
lead to the pilot terminals 44 of the relay. The
20 circuit within the relay is such that current is
supplied to the pilot 4I) as soon as the switch I4
is closed and the relay is energized, but the time
delay in the operation of the relay prevents the
opening of the valve I2 until after the pilot has
25 reached ignition temperature.
Preferably, also,
the circuit of the relay is such that the energiz
ing current for the relay coil or for the heating
coil 23 or both must pass through the electric
pilot 40. This arrangement provides an addi
30 tional safety feature in that the relay cannot be
energized to open the valve I2 unless current is
flowing through the pilot 46.
Suitable relay connections are shown in Fig. 1.
The heating coil 23 is connected at one end di
rectly to the input terminal 32 and at the other
end to one of the contacts 24 and thence by
wires 45 and 46 to one of the pilot terminals 44.
The main relay coil I5 is connected directly to
one of the terminals 32 by means of the wire 41
and to one of the pilot terminals 44 by means of
40
the wire 46. ‘ The supplementary relay coil I5a
is connected at one end to the Wire 46 and at the
other end to one of the contacts 22, the other
` contact 22 being connected to the wire 41. The
other pilot terminal 44 is connected with the in
put terminal 32 by wire 48.
The operation of this system will be clear from
the foregoing description. Assuming that the
switch I4 is closed, either manually or through
any desired control means, the valve I2 is not
50 opened because its circuit cannot be completed
until relay contacts 25 are closed. 'I'he input
current to the relay passes through wires 3| and
35 to the thermostatic device 36, which is closed
if the temperature of the water in the system is
45
55 below ,the desired point, thence through the
safety contacts 31 which are also closed under
normal conditions, and thence to the input
terminal 32. From the input terminal 32 cur
60 rent flows through the main relay coil I5 and
through the heating coil 23 and contacts 24 to
the pilot terminal 44, thence through the pilot
46 and back to the pilot terminal 44, thence
through a wire 48 to input terminal 32 and
thence through wire 29 to the transformer
65
secondary. The pilot 40 immediately begins to
heat up, but the relay is not immediately op
erated to close the valve circuit because of the
time delayed operation explained above. After
to open, interrupting the input circuit to the re
10
lay, whereupon relay contacts 26 open and valve
I2 closes, shutting oi’f the gasto the burner.
However, unless the switch I4 should be opened.
the circuit to the relay will be automatically
closed as soon as the bimetallic element 33 has 15
cooled down suiiiciently to close the contacts 31,
whereupon the relay is again energized and the
operating cycle is again initiated. In the event
that the temperature in the tank becomes ex
cessive, the thermostat 36 is operated to inter
rupt the relay circuit, whereupon the valve I2
20
closes and the gas supply to the burner is shut
oil’. The relay cannot be energized again until
the thermostat 36 has-cooled off suiiiciently to
close its contacts. Should the pilot be burnt 25
out, or should it burn out during operation, the
relay is at once deenergized.
The control system diagrammatically illus
trated in Fig. 3 is substantially similar to that
described above in connection with Fig. 1 and 30
hence the relay and various safety devices are
not shown in detail. In general, this system em
bodies a switch 50 and transformer 5i corre
sponding to the switch I4 and transformer I3,
a relay 52 corresponding to the relay 26 of Fig. 1, 35
and an electrically operated valve 53 corre
sponding to the valve I2 of Fig. 1, the flashback
and thermostatic safety devices not being shown.
This system embodies, however, an additional
safety feature which insures that the valve 53
cannot be opened until the pilot 54 correspond
40
ing to the pilot 40 of Fig. 1 has reached ignition
temperature. This safety device comprises a
pair of normally open contacts 55 connected in
the energizing circuit of the valve in series with
the relay contacts above described, said con 45
tacts 55 being adapted to be closed by any suit
able thermostatic device subject to the tempera
ture of the pilot 54 and adjusted to close the con
tacts when the temperature reaches the proper
point. 'I'his additional safety feature is desir
able to insure against opening of the gas valve
which ‘might take place with the system of Fig. 1
in the event of a short-circuit of the pilot coil 40.
It will be seen that a system embodying the
present invention constitutes a complete and
unitary control system for a gas heater which is
set in operation by the simple closing of a switch
or equivalent operation. As stated above, this
has the advantage that the operation of the 60
heater can be controlled in any desired way in
which the switch I4 can be operated, either auto
matically or manually and at any point at which
it may be desired to control the operation or at
which the switch is located. By leaving the 65
switch closed or by omitting the same, the oper
ation becomes continuous.
Moreover, a system embodying the invention
correlates in unitary manner the functions of
the lapse of a suitable interval necessary for the
coil 23 to heat its bimetallic strip, during which
the pilot 4D reaches ignition temperature, con
tacts 22 are closed and the supplementary coil
I5a of the relay is energized to pick up the
initiating, controlling and stopping the operation 70
75 armature I8, thereby closing the valve contacts
supply valve, and in the absence of some ab 75
of the system as Well as various safety func
tions that rnay be desirable. The valve in the
systems shown in Figs. 1 and 3 opens and closes
to control the flow of gas to the system as a
4
2,137,199 >
normal condition constitutes an automatic oper
ating control for the heater which isV properly
safeguarded to insure reliable and dependable
23 and contacts 24 of Fig. 1) are connected in
series in a circuit one end of which leads to one
of the input terminals 66 and the other end oi'
operation. Thus the provision of a time delay which leads to a terminal 66. The pilot safety
in the operation of the relay contacts insures contacts 69 are connected between this termi
suilicient time before the gas is turned on for nal 68 and the pilot circuit. The circuit of the
the pilot to reach ignition temperature, and the heating coil 66 is therefore completed by way
safety contacts of Fig. 3 provide an additional of the terminal 68, contacts 69. and the pilot
safety feature in the event of a short-circuit of circuit to the terminal 62.
the pilot or «the like. Due to the deenergization
When current is first supplied to this system,
of the supplementary relay coil after the relay ' it p_asses through the main relay coil 63 and 10
operates, the relay is maintained in a condition pilot coil 6I in series', but the circuits of the
such that it returns practically instantaneously heating coil 66 and the supplementary relay coil
to initial position on interruption of the current, 64 are open. As the pilot coil heats up to igni
15 and therefore every interruption of service, how
tion temperature, the contacts 69 close, thereby
ever temporary or accidental, is followed by an
completing the circuit through the heating coil 66
other complete starting cycle. Such automatic and contacts 6l. The operation of the .relay then
operation of the system is not interfered with in proceeds as described above in connection with
any way by the safety controls, and yet the latter Fig. 1. It will be seen that as long as the con
20 are operable in the event of abnormal conditions
tacts 69 are closed, the operation of the system of
to interrupt the current to the relay whereby it Fig. 4 is the same as the operation of the system 20
returns instantaneously to initial position as de
of Fig. 1. However, the relay is inoperative and
scribed above.
'
the system cannot operate unless the contacts 66
Preferably the contacts 55 shown in Fig. 3 are are closed or in other words unless the pilot coil
25 so adjusted that they normally close before the
6| is at ignition temperature.
_.
25
operation of the relay. Also in the _normal op
The provision of an electric control system with
eration of the system the valve 53 closes on de
operating controls and safety controls of the
energization of the relay while said contacts 55 same type enables the provision of a unitary sys
remain closed. Hence in normal operation the tem which is simple and economical and yet
30 circuit is neither made nor broken by contacts reliable and provided with all necessary safe
30
55 while current is flowing.
guards, and at the same time enables the use of
In a system such as that just described with
a single valve to perform the functions of an oper
reference to Fig. 3, the safety contacts associated ating control valve and of a safety control valve
with the pilot device can be utilized to prevent operable under various conditions.
35 opening of the supply valve indirectly by suitably‘
While several systems embodying the invention
connecting them to preventthe operation of the ,have been illustrated and described above, it is to
control relay and thus indirectly of the valve be expressly understood that the invention is not
itself. A system of this type is illustrated in limited to these embodiments but that various
Fig. 4, which except for the safety contacts and changes can be made in the circuit connections,
40 their connection to the relay is the same as that in the operating or safety controls, in the form of
shown in Fig. 1. The relay diagrammatically the several elements employed, etc., without de
shown in Fig. 4 is energized from a'transformer parting from the spirit of the invention. In par
56, the valve 51 having one terminal connected ticular, it will be seen that any suitable type of
directly to the transformer secondary and the relay having time delayed operation can be em
45' other terminal connected to the other side of ployed to close the valve operating contacts after
the transformer secondary through the relay con
a suitable interval in which the pilot reaches igni
tacts 58 corresponding to the relay contacts 25 tion temperature. Any suitable type of safety
of Fig. 1. One of the relay input terminals 59 device can be employed which will effect the inter
is connected directly to the transformer and the ruption of the relay input current in the event of
50 other is connected thereto through a circuit 60
any abnormal condition of the heater which it is
which as indicated by the dotted lines may in
desired to avoid, whether thermostatically oper
clude safety devices such as >the thermostat and ated or otherwise. Also, any suitable type of elec
flashback control of Fig. 1. The pilot coil 6I is trically controlled or operated valve may be asso
c_onnected across the pilot terminals 62, one of ciated with and controlled by the system. Refer
55 which is connected with one of the input termi
ence is, therefore, to be had to the appended
nals as in Fig. 1. The main relay coil 63 and the
supplementary coil 64 are connected in parallel
with each other and across one of the terminals
59 and one of the terminals 62, the circuit of
60 coil 64 including normally open contacts 65 cor
respon-ding to the contacts 22 of Fig. 1.
As thus far described, the system of Fig. 4 is
the same as the system of Fig. 1. As explained
above, the relay operation in Fig. 1 is dependent
65 on the bimetallic element and its heating coil,
and the same is true with the system of Fig. 4.
In the latter system, however, the safety con
tacts associated with the pilot are connected in
series with the heating coil instead of with the
70 valve as in Fig. 3. In this manner the con
tacts act to prevent operation of the relay until
the pilot has reached ignition temperature, the
operation of the valve being in turn controlled
by the relay. To this end the heating coil 66
75 and its contacts 61 (corresponding to the coil
35
40
45
50
55
claims for a definition of the limits of the inven
tion.
What is claimed is:
1. An electrical control system for a gas heater
comprising in combination an electrically con 60
trolled valve, a valve operating circuit including
relay contacts, an electric pilot, a relay holding
coil and a supplementary relay coil necessary for
closing said contacts to open said valve, means for
delaying the energization of said supplementary
coil for a predetermined period after said holding
coil is energized whereby said valve contacts have
time delayed operation, said pilot being con
nected in series with said holding coil, and means
for energizing said relay.
2. An electrical control system for a gas heater
comprising in combination an electrically con
70
trolled valve, a valve operating circuit including
relay contacts, .an electric pilot, a relay holding
coil and a supplementary relay coil necessary for 75
2,137,199
closing said contacts to open said valve, means for
delaying the energization of said supplementary
coil for a predetermined period after said holding
coil is energized whereby said relay contacts have
time delayed operation, an energizing circuit for
said relay coils, said pilot being connected in series
with said holding coil and one or more safety
devices in said relay energizing circuit and
adapted to open the same to deenergize said relay
10 means in the event of an abnormal condition of
' said heater.
5
back in said burner, a second safety device in
said energizing circuit and adapted to open the
same in the event of excessive temperature in
said system, an electrical pilot for igniting said
burner and connected for energization in series
with said energizing circuit, an electrically con
trolled valve, a valve operating circuit including
Si
relay contacts and a pair of normally open con
tacts, means for delaying operation of said relay
for closing said relay contacts, and thermostatic
means responsive to heat from said pilot for clos
3. In a gas heating system, a relay, a relay
energizing circuit, an electric pilot device con
ing vsaid normally open contacts.
nected in series with said relay energizing cir
operating circuit including a pair of normally
cuit, an electrically controlled valve, a valve oper
open contacts, an electric pilot device connected
'
‘7. In a gas heating system, a relay, a relay
ating circuit including relay contacts and a pair ` in series with said relay, an electrically controlled
of normally open contacts, thermostatic means valve, a valve operating circuit incuding relay
responsive to heat from said plot for closing said
normally open contacts, and means for delaying
20 operation of said relay for closing said relay con
tacts.
’
4. In a gas' vheating system, a relay, a relay
energizing circuit, a safety device in said circuit
and adapted to open the same in the event of an
25 abnormal condition of said system, an electric
pilot device connected in series with said `relay
energizing circuit, an electrically controlled valve,
a valve operating circuit including relay contacts
and a pair of normally open contacts, thermo
30 static means responsive to heat `from said pilot
for closing said normally open contacts, and
means for delaying operation of said relay for
closing said relay contacts.
5. In a gas heating system, a gas burner, a>
35 controlling relay, a relay energizing circuit, a
safety 'device in 'said energizing circuit and
adapted to open the same in the event of :Hash
back in said burner, a second safety device in said
energizing circuit and adapted to open the same
40 in the event of excessive temperature in said
contacts, thermostatic means responsive to heat
from said pilot for closing ‘said normally open
contacts, and means for delaying operation of 20
said relay for closing said relay contacts a prede
termined interval after said normally open con
tacts are closed.
8. In a gas heating system, a relay, a relay ener
gizing circuit including a safety device adapted 25
to open said circuit in the event of an abnormal
condition of said system, an electric pilot con
nected in series with said relay, an electrically
controlled valve, a valve operating circuit includ
ing relay contacts, a relay operating circuit in 30
cluding a pair of normally open contacts, thermo
static means responsive to heat from said pilot
for closing said normally open contacts, and
means >for delaying operation of said relay for
closing said relay contacts a predetermined inter
val after said normally open contacts are closed.
9. An electrical control system for a gas heater u
comprising iny combination an electrically con
trolled valve, a valve operating circuit including
relay contacts, a relay holding coil and a supple 40
system, an electrical pilot for igniting said burner ' mentary relay coil necessary for closing said con
and connected in series with said relay energiz-- tacts to open said valve, a control circuit including
ing circuit, an electrically controlled valve, a valve ‘ means having time delayed operation for delaying
operating circuit including relay contacts, and the energization of said supplementary coil for a
45 means for delaying operation of said relay whereby predetermined period after said holding coil is 45
said relay contacts are not closed until after a energized whereby said relay contacts have time
predetermined intervalv following the energiza delayed operation, an electric pilot connected in
series with said holding coil, a pair of normally
tion of said pilot.
6. In a gas heating system, a gas burner, a open contacts in said control circuit, and ther
50 controlling relay, a relay energizing circuit, a mostatic means responsive to heat from said pilot 50
safety device in said energizing circuit and for closing- said normally open contacts.
PAUL L. BE'IZ.
adapted to o_pen the same in the event of ñash
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